Process of improving aluminum alloys



Patented Jan. 17, 1928.

UNITED STAT-Es.

PATENT OFFICE.

WILHELM SANDER, or Essen-Rona, GERMANY, ASSIGNOR 'ro TH. eonnscmain'r A.-G., or ESSEN, GERMANY, AFIRIMI. i

, rnoonss or Imrnovme ALUMINUM annoys.

No Drawing. Application filed November 30, 1926, Serial No. 151,822, and-in Germany October 21, 1925.

This invention relates to processes of improving aluminum alloys. 7

It is known that certain aluminum alloys are unstable in the solid form and undergo 6 molecular internal changes for a time after casting. Their mechanical properties auto matically improve 'by storage for a time at the ordinary temperature after annealing at which may be termed'natural ageing can'b e replaced by ageing at higher temperatures, in which case a still more marked increase in the strength frequently occurs.

30 Prolonged investigations have now. demonstrated that the duration of the period of rest in natural ageing is a material factor;

, that the time when the artificial ageing after the annealing and quenching operations is begun is of great importance. It is possible to control thereby at will the strength and elongation values as well as the malleability and workabilit of the material in the cold state to a conslderable'extent if this period is ascertained by preliminary empirical experiments. Thus for example the artificial ageing or heat treatment can be commenced either immediately after quenching or after an intermediate storage, that is to say at a time during the ordinary ageing at room temperature, when the alloy has not attained its maximum strength values. Finally the heat treatment can also be commenced after completion of the ageing at room temperature, i. e., after the alloy has attained its maximum strength values.

By suitably selecting the aforementioned conditions, it is possible to obtain aluminum alloys containing about 88 to about 98 percent aluminum which exhibit strength values of 36 to 55 kilograms per square millimeter at'elon tions of 18 to 26 per cent, values which fizve not hitherto been obtained by other processes.

Example.

An alloy consisting of 97 per cent alumiannealed at a glowing heat, quenched and subjected to. storage at room temperature. The strength was 35 kilograms per square millimeter and the elongation 15 per cent."

The same alloy was annealed, quenched,

stored 24 hours at room temperature and thereupon for 30 hours at a temperature of 125 C. The strength was found to be 37 kilograms per square millimeter elongation 25 per cent.

Finally the same alloy, after the same preliminary treatment, was aged immediately after quenching, for. 20 hours at 145 C. The strength was found to be 39-40 kilograms per square millimeter and the elongation 20-22 per cent.

and the The presentproeess is applicable to all Experience sium-silicide and similar alloys, that is to 1 say aluminum alloys which contain crystal lizable components adapted to form solid solutions. The process is also applicable to ternary, quaternary and'multiple alloys of aluminum withpthe above-mentioned components. Moreover these alloys may contain other components, particularly difiicultly fusibleelements such as for example, iron, titanium, molybdenum, tungsten and the like for the purpose of increasing their strength and resistance to corrosion.

The above described method of treating the quenched alloy can also be carried out by combining the ageing at ordinary room temperature with an agelng at elevated tem' peratures in suitable manner. These 0 erations can be carried on alternatively an in a suitable sequence.

What I claim is:

1. The process of improving aluminum alloys containing crystallizable constituents capable of'formlng solid solutions with aluminum which comprises'quenching such an alloy from a high and glowing temperature,

ageing to a substantial degree by storage at the ordinary temperature and heat treating at a somewhat higher temperature.

2. Thepr0cess fof im roving aluminum alloys containing crysta izable constituents capable of forming solid solutions with aluminum which comprises quenching such an alloyfrom a high and glowing temperature, ageing at room temperature and heat treating at a somewhat'higher temperaturefthe ageing being substantially complete prior to the heat treatment.

3. The process .of improving aluminum alloys containing 88 to 98 per centaluminum and also containing crystallizable constituents capable of forming solid solutions with aluminum which comprises quenching such ,an alloy from a high and glowing temperature,,ageing at the ordinary temperature for a'substantiallength of time and thereafter ageing at a temperature in the neighborhood 0 145 C.

4. vIn the improvement of aluminum alloys containing 88 to 98 per cent aluminum and WILHELM SANDER. 

